We look at the division of 213689 by 78 
The aim is to understand the frequency of 78 in 213689.

Step 1:
78 goes into 2 0 times with a remainder of 2.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 2 to get 2.
Append the next digit (1) from the dividend to 2 and continue with: 21 / 78

Step 2:
The number 78 fits into 21 0 times, leaving a remainder of 21.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 21 leaves us with 21.
Grab the next digit (3) from the dividend, add it to 21, then carry on: 213 / 78

Advancing to step 3:
78 can be fit into 213 2 times, resulting in a remainder of 57.
The next digit of our result is 2. 
Result so far: 2.0
Deduct 156 from 213 and we're left with 57.
Fetch the next digit (6) from the dividend, attach it to 57 and continue: 576 / 78

On to step 4:
78 goes into 576 7 times with a remainder of 30.
The number 7 becomes the next digit in our result. 
Result so far: 27.0
Subtract 546 from 576 to get 30.
Fetch the next digit (8) from the dividend, attach it to 30 and continue: 308 / 78

Moving on to step 5:
When dividing 308 by 78, we get 3 with a remainder of 74.
Use 3 as the next digit of our solution. 
Result so far: 273.0
If we take 234 away from 308, we end up with 74.
Include the next digit (9) from the dividend after 74, then repeat: 749 / 78

Let's proceed to step 6:
If we divide 749 by 78, we get 9 and a remainder of 47.
Write down 9 as next digit of the result. 
Result so far: 2739.0
The remainder is 47 after subtracting 702 from 749.
Since there are no more digits in the dividend, we add a zero to the remainder making it 470, and continue the process.

Advancing to step 7:
78 can be fit into 470 6 times, resulting in a remainder of 2.
The number 6 becomes the next digit in our result. 
Result so far: 2739.6
The remainder is 2 after subtracting 468 from 470.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Advancing to step 8:
20 divided by 78 is 0 with a remainder of 20.
The number 0 becomes the next digit in our result. 
Result so far: 2739.6
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Moving on to step 9:
78 can be fit into 200 2 times, resulting in a remainder of 44.
Write down 2 as next digit of the result. 
Result so far: 2739.602
If we subtract 156 from 200, we get 44.
Since there are no more digits in the dividend, we add a zero to the remainder making it 440, and continue the process.

Going ahead to step 10:
78 can be fit into 440 5 times, resulting in a remainder of 50.
Use 5 as the next digit of our solution. 
Result so far: 2739.6025
Subtracting 390 from 440 leaves us with 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 500, and continue the process.

Going ahead to step 11:
500 divided by 78 is 6 with a remainder of 32.
Write down 6 as next digit of the result. 
Result so far: 2739.60256
If we take 468 away from 500, we end up with 32.
Since there are no more digits in the dividend, we add a zero to the remainder making it 320, and continue the process.

On to step 12:
When dividing 320 by 78, we get 4 with a remainder of 8.
Use 4 as the next digit of our solution. 
Result so far: 2739.602564
Subtract 312 from 320 to get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Moving on to step 13:
78 can be fit into 80 1 times, resulting in a remainder of 2.
Record the quotient 1 as the next digit in the result. 
Result so far: 2739.6025641
Subtract 78 from 80 to get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Moving on to step 14:
78 can be fit into 20 0 times, resulting in a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 2739.6025641
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

The final outcome is 2739.6025641, with a leftover of 2e-08.